1. Field of the Invention
This invention relates to a photoelectric device which is used in the storage mode, and more concretely to the structure of a photosensitive panel which can be employed for the photoconductive target of an image tube, etc.
2. Description of the Prior Art
As a typical example of a photoelectric device which is used in the storage mode, there is a photoconductive image tube shown in FIG. 1. It is constructed of a light-transmitting substrate 1 usually termed "faceplate", a transparent conductive film 2 serving as a signal electrode, a photoconductor layer 3, an electron gun 4, and an envelope 5. In operation, an optical image formed on the photoconductor layer 3 through the faceplate 1 is photoelectrically converted and is stored as a charge pattern in the surface of the photoconductor layer 3, and the charge pattern is read in time sequence by a scanning electron beam 6.
Ordinarily, a beam landing layer 7 is disposed on the surface of the photoconductor layer 3 for the purposes of preventing the inversion of the polarity of the surface charges, blocking the injection of electrons from the scanning electron beam, and so forth.
An important property required of the photoconductor layer 3 at this time is that the charge pattern does not decay due to diffusion within a time interval in which a specified picture element is scanned by the scanning electron beam 6 (i.e., within a storage time).
Examples of such photoconductive targets are described in:
U.S. Pat. No. 3,346,755 PA1 U.S. Pat. No. 3,350,595
The use of amorphous silicon for the photoconductor layer 3 is described in, for example, British Specification No. 1,349,351 (E. M. I. Limited).